This application relates generally to medical instruments and methods of use to remove occlusive material from a vessel, duct or lumen within the body of a living being.
Catheter instruments have been suggested or disclosed in the patent literature for effecting non-invasive or minimally invasive revascularization of occluded arteries. For example, in U.S. Pat. No. 4,445,509 there is disclosed a recanalization catheter designed specifically for cutting away hard, abnormal deposits, such as atherosclerotic plaque, from the inside of an artery, while supposedly preserving the soft arterial tissue. That recanalizing catheter includes a sharp-edged, multi-fluted, rotating cutting tip mounted at the distal end of the catheter and arranged to be rotated by a flexible drive shaft extending down the center of the catheter. The rotation of the cutting head is stated as producing a xe2x80x9cdifferential cuttingxe2x80x9d effect, whereupon relatively hard deposits are cut away from relatively soft tissue. Suction ports are provided to pull the hard particles produced by the cutting action into the catheter for removal at the proximal end thereof so that such particles do not flow distally of the catheter where they could have an adverse effect on the patients"" body.
In U.S. Pat. No. 4,700,705, which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there are disclosed and claimed catheters and methods of use for effecting the opening of a vessel, duct or lumen, such as the opening of a atherosclerotic restriction (partial or total occlusion) in an artery. These catheters are elongated flexible members of sufficient flexibility to enable them to be readily passed through the body of the patient to the situs of the atherosclerotic plaque in the artery to be opened. A working head is mounted at the distal end of the catheter and is arranged for high-speed rotation about the longitudinal axis of the catheter. In some embodiments the catheter may eject fluid at the working head to expedite the restriction-opening procedure.
In U.S. Pat. No. 4,747,821, which is also assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there is disclosed and claimed other catheters particularly suited for revascularization of arteries. Each of those catheters includes a rotary working head having at least one non-sharp impacting surface to effect material removal without cutting. Moreover, those catheters are arranged to eject fluid adjacent the working head to expedite the revascularization procedure. In particular, the rotation of the working head produces a powerful, toroidal shaped vortex contiguous with the working head which has the effect of recirculating any particles that may have been broken off from the material forming the arterial restriction so that the working head repeatedly impacts those particles to reduce their size.
In U.S. Pat. No. 5,042,984, which is also assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there are disclosed and claimed catheters whose working heads include impacting surfaces of differing aggressiveness which may be selectively brought into engagement with the restriction to be opened. Such catheters also make use of exiting jets of liquid as described above.
Other atherectomy devices for enlarging an opening in a blood vessel have been disclosed and claimed in the following United States patents: U.S. Pat. No. 4,589,412 (which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein); U.S. Pat. Nos. 4,631,052; 4,686,982 (which is assign ed to the same assignee as this invention and whose disclosure is incorporated by reference herein); U.S. Pat. No. 4,749,376 (which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein); U.S. Pat. Nos. 4,790,813; 5,009,659; 5,074,841; 5,282,484; 5,366,463; 5,368,603; 5,402,790; 5,423,742; and 5,429,136.
Some rotary atherectomy devices are in use in this country for revascularizing occluded arteries. However, their use is limited to some very selected applications. Thus, in many instances a vascular occlusion of a coronary artery can only be treated by coronary bypass surgery wherein a graft, e.g., a saphenous vein section and/or mammary artery section, is surgically shunted across the occluded coronary artery. Unfortunately a significant percentage of bypass surgical grafts become re-occluded over time. Thus, the re-occluded graft has to be either bypassed by another graft (i.e., second bypass surgery), or the re-occluded graft has to be revascularized (i.e., its lumen reopened) by some intravascular procedure. If the occluded graft is not totally occluded, balloon angioplasty may be indicated to reopen the graft. Where, however, the graft is totally occluded or heavily occluded by frangible deposits balloon angioplasty is.unavailable. Thus, if revascularization of such a graft is desired, resort may be to rotary atherectomy.
One currently available rotary atherectomy device is the ROTOBLATOR(copyright) System of Heart Technology, Inc. That system utilizes a catheter having a diamond coated elliptical burr which is rotated at a high rate of speed, e.g., up to 190,000 rpm. The burr serves to break the atherosclerotic plaque into fine particles which are allowed to remain in the patient""s body for disposal by the patient""s reticuloendothelial system.
As is known to those skilled in the art, one problem with a rotary atherectomy device is that unless the debris produced is so small and benign that it can be left within the patient""s vascular system there must be some means to ensure that the debris does not flow upstream into the aorta during the procedure or into the downstream artery graft at the break-through point when the device comes out the distal side of a total occlusion, since either action could present a significant hazard to the patient. In particular, the former route risks stroke, the later route risks local ischemia of heart muscle when debris blocks off small arteries.
Thus, the collection and/or aspiration of debris produced during the revascularization of occluded arterial bypass grafts or other blood vessels is getting considerable attention in the medical arts. For example, Possis Medical, Inc., the assignee of U.S. Pat. Nos. 5,370,609 and 5,496,267, provides catheter devices designated as the ANGIOJET Rapid Thrombolectomy System and the ANGIOJET Rheolytic Thrombolectomy System. These devices are presumably constructed in accordance with those patents and are believed to be presently undergoing clinical trials. The catheter devices disclosed in those patents utilize high velocity jets of saline to abrade the blockage. In Particular, the patents disclose utilizing the momentum of the saline jets to create a local vacuum to entrain any particulate material produced by the revascularization procedure, with the momentum and the local positive pressure being sufficient to carry the saline and debris to a return collection bag.
Another atherectomy device which is currently undergoing clinical trials is the Coronary TEC(copyright) System of Interventional Technologies, Inc. That device is believed to be the subject of U.S. Pat. No. 5,224,945, and basically comprises a catheter having a working head with microtome sharp blades for cutting plaque circumferentially. The excised plaque is extracted by suction through a central lumen in the catheter into an exteriorly-located vacuum bottle. No control of the quantity of flow of the debris-carrying fluid from the catheter is disclosed.
U.S. Pat. No. 5,030,201 (Palestran) discloses a system including an expandable atherectomy catheter arranged to be rotated to cut through an occluded artery to revascularize it. The atherectomy catheter includes an expandable cutting head having plural elongated cutting members which are mounted on a flexible torque tube incorporating a vacuum or aspiration system for retrieval of excised material. The cutting head is arranged to be rotated to cause the elongated members to cut away atheromatous material or blood clots. The atherectomy catheter is arranged to be inserted into the blood vessel through a coaxial delivery catheter, also forming a part of the system. The mechanism for aspirating particles of atheromatous material or blood clots removed by the elongated cutting members is disclosed as being in the form of a vacuum port provided at the proximal end of either the delivery catheter, the atherectomy catheter or a xe2x80x9cretracting catheterxe2x80x9d which also constitutes a part of the system. Saline solution or some other irrigant is infused through one of the catheters of the device that is not being used for aspiration. The infusion rate of the saline solution is balanced with the aspiration rate to avoid any net removal of fluid from the vessel. In particular, the patent teaches that by balancing the infusion rate of the saline solution to the aspiration rate, the net removal of fluid from the vessel can be brought close to zero, thereby minimizing blood loss.
While the balancing of the infusion and aspiration flow rates to minimize blood loss may be desirable, such action does not insure positive removal of all debris produced during the revascularization procedure.
Accordingly, a need exists for apparatus and a method of use to revascularize partially or totally occluded blood vessels, while positively assuring that any particles produced during the revascularization procedure are removed from the patient""s body. In the case of partially or totally occluded coronary bypass grafts, a need exists for intravascular atherectomy apparatus and methods of use for effectively producing a lumen through the occlusion for the free flow of blood, without the risk that any debris produced during the lumen opening procedure will enter into the aorta or downstream of the occlusion once it has been crossed or opened.
A system for opening a lumen in an occluded blood vessel, e.g., a coronary bypass graft, of a living being""s vascular system located downstream of another blood vessel, e.g., the aorta, from which blood will flow to the occluded blood vessel. The system basically comprises a guide catheter, a lumen-opening catheter, a debris blocking member, and a fluid flow system.
The guide, catheter has a distal end portion and at least one blood entrance port located proximally of the distal end portion. The lumen-opening catheter extends through the guide catheter to establish a fluid flow passageway therebetween and has a working head, e.g., a rotatable impacting member, for location immediately adjacent the occlusive material within the occluded blood vessel portion. The working head is arranged for operating on the occlusive material, e.g., repeatedly impacting it, to open a lumen for the freer flow of blood therethrough. Some debris may be produced by the operation of the working head.
The debris blocking member is located distally of the working head to prevent debris from flowing distally thereof.
The fluid flow system is arranged to introduce an infusate liquid at a first flow rate adjacent the working head and to withdraw that liquid through the passageway between the guide catheter and the lumen opening catheter at a second and higher flow rate to create a differential flow adjacent the working head, whereupon debris produced by the operation of the working head is withdrawn by the differential flow and flows with the liquid proximally through the passageway for extraction.
The blood entrance port in the distal end portion of the guide catheter is in communication with the passageway between the guide catheter and the lumen opening catheter, whereupon blood from the patent blood vessel portion may enter for merger with the liquid and debris flowing through that passageway.
The debris blocking member is an inflatable balloon is provided at the distal end of the instrument to physically block the egress of any debris downstream of the apparatus. Perfusion means is preferably provided to inflate the balloon and to oxygenate downstream tissue when the balloon is inflated.